Fraction of myosin cross-bridges bound to actin in active muscle fibers: estimation by fluorescence anisotropy measurements.
AUTOR(ES)
Burghardt, T P
RESUMO
Time-resolved and steady-state fluorescence anisotropy measurements from fluorescence-labeled myosin cross-bridges in single glycerinated skeletal muscle fibers in rigor, relaxed, MgADP-induced, and contracting states have been made in order to estimate the fraction of actin-bound cross-bridges in active muscle. When the plane of polarization of the excitation light is perpendicular to the fiber axis and its propagation vector has a component parallel to this axis, actin-bound cross-bridge states, such as rigor and MgADP-induced, have time-zero and steady-state anisotropies that are substantially lower than has the relaxed state. This difference provides a means of determining the fraction of cross-bridges bound to actin in active isometric fibers, by comparing the fluorescence anisotropy from active fibers with the anisotropy from bound and unbound cross-bridges in static states. By assuming that the active cross-bridges are either bound (in the manner of rigor or MgADP-induced states) or relaxed, we estimate that greater than 80% of the cross-bridges are actin-bound in active isometric fibers.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=390939Documentos Relacionados
- Force generation and work production by covalently cross-linked actin-myosin cross-bridges in rabbit muscle fibers.
- X-ray diffraction studies of cross-bridges weakly bound to actin in relaxed skinned fibers of rabbit psoas muscle.
- Effect of negative mechanical stress on the orientation of myosin cross-bridges in muscle fibers.
- Radial equilibrium lengths of actomyosin cross-bridges in muscle.
- Exchange of ATP for ADP on high-force cross-bridges of skinned rabbit muscle fibers.